Electric power generation



310-11 SR SEARCH ROOM FIPBSOZ OR 514$249 Sept. 15, 1964 J. M. LAFFERTYETAL 3,149,249

ELECTRIC POWER GENERATION Filed April 17, 1961 Inventor's James M.Lafler'ty James D. Cob/fie Thomas A Vanderallbe United States PatentOffice 3,149,249 Patented Sept. 15, 1964 3,149,249 ELECTRIC POWERGENERATION James M. Laiferty, Schenectady, James D. Cobine, Rexford, andThomas A. Vanderslice, Scotia, N.Y., assignors to General ElectricCompany, a corporation of New York Filed Apr. 17, 1961, Ser. No. 103,3048 Claims. (Cl. 31011) This invention relates to a method and apparatusfor generating electric power, and, more particularly, to an improvedmethod and apparatus for generating electric power by the interaction ofa moving conducting fluid and a magnetic field.

Conventional rotating devices for generating electricity are based onthe principle of first converting heat energ to rotational mechanicalenergy, typically in a prime mover such as a steam turbine, and thenconverting the mechanical energy into electrical energy by driving ametallic conductor through a magnetic field. For economical operation ofsuch turbine powered generating systems, high thermal conversionefficiencies in the steam turbine are imperative. The variousimprovements in turbine efficiencies that have been effected in the pasthave been achieved by operating at ever higher temperatures andpressures. As these rise, the problems they generate multiply so rapidlythat a limit is quickly reached in what may be accomplished by furtherincreases in operating temperatures and pressures. Probably the greatestdifficulties arise in the materials area, since the mechanical stresseson moving parts such as turbine blades, shafts, etc., becomeprogressively more severe as operating temperatures and pressuresincrease. a diminishing returns effect has set in and improvements inefficiency have been achieved in smaller and smaller increments and athigher and higher costs. Many of these difficulties can be avoided andradical improvements in conversion efficiencies can be effected by completely eliminating those elements which limit performance and devisinga system that does not have any moving mechanical components.

To this end, it has been proposed to generate electricity by abstractingenergy from a moving conducting fluid, preferably a gaseous one, as itpasses through a magnetic field without employing rotating or movingparts merely by impressing a pressure difference on the fluid.Mechanical prime movers, such as turbines are, therefore, no longernecessary and a generating system without any moving parts is feasible.The body of scientific knowledge dealing with the interaction of aconducting gaseous fluid with a magnetic field is commonly known asmagnetohydrodynamics (usually abbreviated to MHD) and all subsequentreferences in this specification to the generation of electrical powerby the interaction of a conducting fluid and a magnetic field will be tomagnetohydrodynamic generation or MHD generation.

A typical example of an MHD generating system as conceived by previousworkers in the field is described in detail in Patent No. 1,717,413,issued June 18, 1929 to R. Rudenberg, which contemplates bringing a gasstream to a conducting condition by heating it to a temperature at whichit becomes partially ionized. The ionized gas stream is driven through amagnetic field by a pressure difference, causing an electromotive force(E.M.F.) to be generated in the gas. Under the influence of this suchcharged particles as are present in the gas are deflected to a pair ofelectrodes causing a unidirectional or direct current to flow through anexternal load circuit connected to the electrodes.

An alternating current MHD generator is described in the copendingapplication of Emmeth A. Luebke, Serial No. 39,590, filed July 29, 1960,and assigned to the as Consequently,

signee of the present invention. In that device the conducting gaseousmedium is driven along an annular path through a varying radial magneticfield and the interaction of the moving conducting medium with thevarying magnetic field produces a circulating current within theconducting medium itself. The circulating current induces a time varyingoutput electromotive force in an output coil wound around the flow path.

Both of these types of MHD generating systems are characterized bydifficult maintenance problems, because of the rugged environment towhich the construction ma terial is exposed. The electrodes andconfining walls for the conducting gaseous medium are exposed totemperatures of several thousand degrees Kelvin, which are necessary toobtain the required ionization of the gas. Thus far, it has beenimpossible to increase the power output by increasing the degree ofionization because of the deleterious effect on the electrodes and/ orthe wall material when the temperature of the gaseous conducting me diumis further raised. Therefore, it is a primary object of this inventionto provide a method and means by which the power output ofmagnetohydrodynamic generators may be increased without increasing thetemperature of the gaseous conducting medium.

Another object of the invention is to provide a method and means forgenerating electrical power in an MHD r apparatus in which the degree ofionization is not dependent solely upon the temperature to which thegaseous conducting medium is heated.

It is another object of the invention to provide a method and means forincreasing the degree of ionization and for maintaining the ionizationat a higher level and for a longer time than heretofore possible, thusimproving the performance of the generator.

Other objects and advantages will become apparent as the description ofthe invention proceeds.

Before discussing MHD generation according to the" principles of thisinvention, it will be useful to review some pertinent physicalproperties of gaseous fluids; the conditions under which they becomeconducting; and the manner in which this conductive condition may beachieved to facilitate interaction with a magnetic field. The basicproperties of pure gases or of gas mixtures, such as air, are such thatunder normal circumstances of temperature and pressure the conductivityof the gas is so low that for all practical purposes the gas isnonconducting and no interaction with a magnetic field is possible. Toachieve any significant results, the conductivity of the gaseous fluidmust be increased in some manner. The preferred method of enhancing thegas conductivity is by partially ionizing the gas, causing a fraction ofthe gas molecules to lose one or more electrons. The resulting chargedparticles are free to drift through the gas and may give rise to currentconduction by interaction with a magnetic field.

The gas may be ionized in any one of several ways, as by thermalionization, electric field ionization, photoionization, etc. Because ofthe relative ease and effectiveness with which it may be carried out,the preferred method used thus far in MHD generating systems is bythermal ionization, i.e., adding heat energy to the gas until some ofthe gas molecules lose electrons. The thermal ionization process is,however, severely temperature dependent; i.e., there is a thresholdtemperature range below which insuflicient ionization takes place. Theionization energy, by which is meant the thermal energy increment whichmust be added to the molecules to initiate ionization and tear loose oneor more of its electrons, is quite high for most gases. Common gases,such as air, C0, C0 as well as noble gases, show no useful ionizationunless the gas is heated above a temperature of approximately 3500 K.(5800 F.). It will be appreciated that the problems involved in heatingthe gas to an operating temperature, which must be even higher than theionization temperature of 3500 K., are substantial both in terms of themagnitude of the effort required to heat the gas and in terms of theproblem of finding materials capable of withstanding such temperatures.

Fortunately, these difliculties may be reduced by a technique whichsubstantially lowers the critical threshold temperature for ionization.It has been found that by adding a small amount, in the range of 0.011%by volume, of some easily ionizable material, such as an alkaline metalvapor, for example, the ionization temperature is reduced by as much as40-50%.

For example, by seeding clean air through the addition of 1% or less byvolume of potassium vapor, the critical ionization temperature isreduced from 3500 K. (5800 F.) to 2000 K. (3600 F.). Cesium (Cs),rubidium (Rb), potassium carbonate (K C0 and cesium carbonate (CsCO areadditional examples of alkaline metal vapors or compounds which areeffective for this purpose.

The actual choice of seed material concentration must be determined bycalculation and/or experimental tests for the specific conditions ofeach MHD generator in accordance with the criteria which are taught bythis invention. In most designs of practical interest, the ratio of seedmaterial to working gas atomic concentration should be in the range 10-to 10- For a more thorough discussion of electrical conductivity andionization phenomena, reference is hereby made to the text Introductionto the Theory of Ionized Gases by J. L. Delcroix, IntersciencePublishers, Inc., New York, 1960.

Briefly stated, the present invention contemplates using anothercomponent in the gas mixture in addition to the seed material toincrease the degree of ionization and to maintain the ionization at ahigh level for a relatively long period of time. The requiredcharacteristic of the component is that it have one or more metastableexcited states with excitation energy comparable to the ionizationenergy of the seed material. Thus, upon collision with an un-ionized ornormal atom of seed material as the gaseous mixture passes through thegenerator, the energy of excitation of the metastable state istransferred to the seed material atom causing it to become ionized.

The novel features which are believed to be characteristic of theinvention are set forth in the appended claims. The invention itself,however, together with further ob jects and advantages thereof, may bestbe understood by reference to the following description taken inconjunction with the accompanying drawings, in which:

FIGURE 1 is a schematic illustration of a direct current MHD generatoruseful in understanding the present invention;

FIGURE 2 is a diagram useful in understanding the invention; and

FIGURE 3 is a diagrammatic longitudinal sectional view of a generatorconstructed in accordance with the invention.

In FIGURE 1, a conventional prior art D.C. MHD arrangement is shown asincluding an elongated rectangular fluid passage or duct 1, extendinginto the plane of the paper. Metallic electrodes 2 and 3 are disposed inthe duct and are connected to a load circuit which, for simplicity ofexplanation and illustration, is shown as a simple variable resistance4. The duct is disposed between the pole pieces 5a and 5b of a suitablemagnet. If the direction of gas flow is into the plane of the paper anda magnetic field of constant flux density is applied at right angles tothe direction of flow, as illustrated by the arrows labeled B, an isgenerated in the conducting gas at right angles both to the field and tothe direction of flow. This E.M.F. acts on the free electrons in theionized gas and causes an electron current to flow between electrodes 2and 3 and through the load 4 in the direction shown by the arrow I. Ifthe direction of gas flow is reversed, the current flow is in theopposite direction.

In magnetohydrodynamic generators, it is known that the amount ofcurrent flowing between the electrodes in a direct current device, orthe amount of current generated in an output winding in an alternatingcurrent device, is dependent upon a number of factors. Among these arethe degree of ionization of the gaseous working medium, the strength ofthe magnetic field applied across the duct, the velocity and density ofthe gaseous working medium as it passes through the magnetic field, andvarious parameters of duct and electrode configuration. Until now, ithas been presumed that the degree of ionization of the gaseous workingmedium was dependent strictly upon the temperature to which the mediumwas heated. This, of course, placed severe demands upon the materials ofwhich the duct and electrodes were constructed, because they wereexposed to temperatures of several thousand degrees Kelvin from a gaspassing therethrough with a velocity at least equal to that of the speedof sound. As to the other parameters affecting the generation, there arephysical limitations on the strength of the magnetic field that may beemployed inasmuch as the amount of iron and/ or copper required becomesprohibitively large; of course, the velocity of the gaseous conductingmedium as it passes through the duct cannot be increased indefinitely,again because of the materials problem.

It is known that atoms may exist in various excited states depending onthe amount of energy that they have absorbed. For example, FIGURE 2illustrates only four of the large number of states to which an atom ofmercury may be excited. A normal ionized mercury atom will have absorbed10.38 electron-volts (e.v.), but the atom may exist in intermediatestates where it has absorbed 4.66, 4.86 or 5.43 e.v. It is anothercharacteristic of such atoms that they can normally fall from oneexcited state to a less excited state, while giving up the difference inenergy in the form of light, which may be either in the visible spectrumor outside it. For example, the familiar yellow color of a sodium-vaporarc lamp occurs as the atoms fall from their lowest excited state totheir normal unexcited state.

It is also known that changes from an excited state to a less excitedstate are governed by physical rules. For example, where the orbitalmomentum of an atom is a vector L that represents the vector sum of allthe 1 vectors of its electrons, the total spin moment S of an atom isthe vector sum of all the s vectors of the electrons of that atom andthe vector sum J of S and L, represents the total angular momentum ofthe atom, transitions between excited states will most probably takeplace where the quantized value of I changes by +1, l, or 0 and notbetween two levels where 1:0 for both. Thus, in the diagram of FIGURE 2,it is seen that a mercury atom cannot drop from its J=2 level to itsnormal un-ionized or zero state or from its J=0 (4.66 e.v.) state to itszero state, but it can drop from its J=1 state to its zero state andemit light having a wavelength of 2537 Angstom units (A). Furthermore,for another physical reason which prohibits radiative transitionsbetween certain energy levels, a mercury atom cannot by itself drop fromits 5.43 e.v. level to its 4.86 or 4.66 e.v. levels. These levels fromwhich transitions to lower energy levels are prohibited or arerelatively unlikely to occur are called metastable levels or states. Fora good explanation of energy levels and the various states, reference ismade to the book Gaseous Conductors by James D. Cobine, published byDover Publication, Inc., New York, N.Y., 1958, and particularly toChapter III thereof. The various energy level values set forth hereinare also taken from that book.

Once an atom is in a metastable level, it must remain there until theatom has a collision with another particle. If an electron havingsufficient energy strikes a metastable atom, it may raise the atom thatis in the metastable state to a higher energy level from which it canreturn to the normal state. When atoms of other elements are present,the excess energy of the metastable atom may be given up by exciting orionizing one of the other atoms. Because the encounters by which ametastable atom can change its energy level are special and relativelyunlikely to occur, the average life of a metastable atom is relativelylong seconds) compared to the average life of an atom in a normalexcited state (10- seconds).

The present invention contemplates using a component in the gaseousworking medium, in addition to the seed material, which component hasone or more metastable excited states with excitation energy comparableto the ionization energy of the seed material. If such a material isincorporated into the gas mixture of the MHD generator, then themetastable states of this material may be excited by electron impact orby means of a supplemental electric field such as produced by an aredischarge. They will then, with high probability, maintain theirexcitation until they collide with an un-ionized seed material atom,whereupon the energy of excitation of the metastable state will betransferred to the seed material atom and cause it to become ionized.

Typical combinations of seed material and third com- ;ponent materialare cesium as the seed material and mercury, cadmium, or zinc vapor isthe third component. Rubidium or potassium as the seed material andmercury vapor as the third component is also a favorable com- I binationsince the metastable level excitation in mercury (4.66 e.v.) iscomparable to but slightly above the ionization potentials of rubidium(4.18 e.v.) or potassium (4.34 e.v.).

A typical over-all atomic composition of the gas mixture would be anadmixture of 1% mercury vapor and l0 cesium vapor to helium or othernoble gas. This illustrates the preferred region of operation in thatthe third component concentration is considerably larger than the seedconcentration but small compared to the working gas concentration.

An important benefit to be gained from the use of a third componentmaterial containing metastable states is that the metastable states ofinterest generally occur in combination with a state which emits strongresonance radiation. For example, as pointed out with reference toFIGURE 2, in mercury the metastable states are the 1:0 and 1:2 membersof a triplet, the third member of which is 1:1 state which emits theresonance line at 2537 A. This resonance radiation allows the mercuryexcitation energy to be spread out over a relatively large volume sincethe radiation from one mercury atom is absorbed by other mercury atomsin the gas and then transferred to metastable states of mercury byinelastic collision of mercury atoms and other atoms. This means thatthe ionization becomes fairly uniform over the volume of the gas. Thisresonance radiation does not constitute a serious drain of energy fromthe system since it is strongly self-absorbed. This distance whichenergy is transported by the resonance radiation is small compared tothe dimensions of the MHD generator duct, but large enough to smooth outlocal inhomogeneities in the ionization density. This effect, therefore,not only facilitates the initial establishment of a relatively uniformdegree of ionization but furthermore aids in maintaining uniformity ofionization throughout the gas as it passes through the MHD generator.

The persistence of ionization in the working gas, which is necessary inengineering design, is greatly enhanced by the presence of themetastable component in the gas by virtue of its ability to causecontinuing ionization of the seed material as it flows through thechannel through collisions with metastable atoms and also by virtue-ofits ability to spatially distribute electronic excitation energy byresonance radiation as described above.

FIGURE 3 illustrates diagrammatically a direct current MHD generatorconstructed in accordance with the principles of the invention. Althougha direct current generator is illustrated, it is to be understood thatthe principles of the invention are equally applicable to an alternatingcurrent generator.

A flow path for a moving conducting gas is provided by a rectangularlyshaped duct 10, which is bolted or otherwise fastened by means offlanges 11 to suitable inlet and outlet conduits 12 and 13, throughwhich the gaseous working medium enters and leaves the duct 10. The duct10 is also provided with two electrodes 14 (only one of which is shown)made of a suitable conducting material such as carbon, which are locatedwithin the magnetic field produced by a magnetic structure 16 andbetween which the external load (not shown) is connected.

The duct 10 and the conduits 12 and 13 include a high temperature lining17 fastened to a supporting wall 18 of a non-magnetic material such asstainless steel. The high temperature lining 17 is exposed to the hotflowing gas and must, therefore, be fabricated of a temperatureresistant material. Refractory materials such as magnesium oxide andzirconium oxide, for example, are particularly suitable as liningmaterials. Many other refractory materials having similar temperatureresistant properties are available and may be used in constructing thelining 17. The various thermal coefficients of expansion of thematerials are such that substantial linear expansion under expectednormal operating temperatures can be anticipated. High temperaturelining 17 must, therefore, be constructed to allow for this expansionand is formed of a plurality of small interlocking pieces 20, which havesufficient clearance to accommodate the thermal expan- SlOIl.

The magnetic assembly 16, referred to previously, is of laminated ironconstruction and is excited from a suitable energy source to impress asteady magnetic field across the rectangular duct 10 parallel to theplanes of the electrodes 14. The assembly 16 includes a field producingwinding (not shown) and pole pieces 21 and 22.

The heated conducting gas, which is the working medium of the MHDgenerator, is brought to the rectangular duct 10 through inlet conduit12 which communicates with a combustor (not shown) or other source ofheat, where the gas is brought to the desired temperature. Before thegas enters the duct 10, a component such as mercury, cadmium, or zincvapor having one or more metastable states, is injected into it throughan injector unit, shown generally at 23. The metastable state of thecomponent may conveniently be excited by a suitable arc dischargebetween a pair of electrodes 24 and 25 located downstream of theinjector unit 23. When the electrodes 24, 25 are connected to a suitablesource of electric power (not shown) and a discharge takes place betweenthem, the electric field produced by the discharge raises the energylevel of the atoms to a metastable level, in which state the atomsremain as they travel downstream with the gaseous working medium.

Located downstream of the injector unit 23 and the electrodes 24, 25 andnear the entrance to the duct 10 is another injector unit, showngenerally at 26, through which seed material is injected into thegaseous mixture. As previously mentioned, the seed material ispreferably an easily ionizable alkaline metal vapor, such as cesium,potassium, or rubidium, having an ionization potential approximatelyequivalent to and preferably less than the metastable level excitationof the other component.

As the atoms of the component injected through the injector unit 23travel downstream in their metastable states, they collide withun-ionized atoms of seed material, whereupon the energy of excitation ofthe metastable states is transferred to the seed material atoms, thusionizing them. Because the life of a metastable atom is relatively longcompared to that of an ionized atom and because the seed materialinjector unit 26 is located close to the duct 10, ionization willcontinue within the duct 10 thus materially improving the performance ofthe generator.

It is pointed out that the metastable component should have its energylevel raised to a metastable level before the seed material is injectedinto the mixture. This is because the seed material has a lowerionization potential than the metastable component and, if the seedmaterial passes through the field produced by the arc discharge alongwith the metastable component, the seed material will be ionized but themetastable component will not in all probability have its energy levelraised to a metastable level.

It is apparent that many changes and modifications will suggestthemselves to one skilled inthe art. For example, the working gas itselfmay be of a type having one or more metastable states. In that event,the injector unit 23 may be eliminated since there is no need to add athird component to the gaseous mixture.

Although the invention has been illustrated and described as applied toa particular type of direct current magnetohydrodynamic generator, it isequally applicable to all types of MHD generators, such as a Hall typeor segmented electrode type of DC. generator or to all alternatingcurrent MHD generators. Furthermore, it may be applied to both open andclosed cycle systems. Therefore, the invention is to be considered aslimited only by the scope of the appended claims.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A method of generating electric power, which comprises the steps ofconducting a gaseous fluid along a flow path, injecting into saidgaseous fluid a first material Whose atoms have at least one metastableenergy level, raising the energy level of atoms of said first materialto their metastable level, injecting an easily ionizable second materialinto said gaseous fluid after said atoms of said first material havebeen raised to a metastable level whereby atoms of said second materialare ionized by collisions with atoms of said first materialin saidmetastable level, and passing the gaseous fluid mixture through amagnetic field whereby electric current flows through said gaseousmixture.

2. A method of generating electric power, which comprises the steps ofconducting a gaseous fluid alongla flow path, injecting into saidgaseous fluid afirst material whose atoms have at least one metastableenergy level, raising the energy level of atoms of said first materialto a metastable level, injecting into said gaseous fluid after saidatoms of said first material have been raised to said metastable levelan ionizable second maprises the steps of conducting a gaseous fluidalong a flow path, injecting into said gaseous fluid a first materialwhose atoms have at least one metastable energy level to which saidatoms are raised after injection of said first material into saidgaseous medium, injecting into said gaseous fluid after said atoms ofsaid first material have been raised to said metastable level anionizable second material having an ionization energy level comparableto said metastable energy level of said first material, whereby atoms ofsaid second material are ionized by collisions with atoms of said firstmaterial in said metastable level, and passing the gaseous fluid mixturethrough a magnetic field whereby electric current flows through saidgaseous mixture.

5. In a magnetohydrodynamic generator, the combination comprising meansdefining a flow path for a gaseous fluid, means for injecting into thegaseous fluid a first 'material whose atoms have at least one metastableenergy level, means for raising the energy level of atoms of said firstmaterial to said metastable level, and means for injecting an easilyionizable second material into the gaseous fluid after said atoms ofsaid first material have been raised to said metastable level, wherebyatoms of said second material are ionized by collisions with atoms ofsaid first material in said metastable level.

6. In a magnetohydrodynamic generator, the combination comprising meansdefining a flow path for a gaseous fluid, means for injecting to thegaseous fluid a first material whose atoms have at least one metastableenergy level, means for raising the energy level of atoms of said firstmaterial to said metastable level, and means for injecting into thegaseous fluid after said atoms of said first material have been raisedto said metastable level first material, whereby atoms of said secondmaterial are ionized by collisions with atoms of said first material insaid metastable level.

. 7. In a magnetohydrodynamic generator, the combination comprisingmeans defining a flow path for a gaseous fluid, means for injecting intothe gaseous fluid a first material whose atoms have at least onemetastable energy level to which level said atoms are raised in thegaseous fluid, and means for injecting an easily ionizable secondmaterial into the gaseous fluid after said atoms of said first materialhave been raised to said metastable level, whereby atoms of said secondmaterial are ionized by collisions with atoms of said first material insaid metastable level.

8. In a magnetohydrodynamic generator, the combination comprising meansdefining a flow path for a gaseous terial having an ionization energylevel comparable to said metastable energy level of said first material,whereby atoms of said second material are ionized by collisions withatoms of said first material in said metastable level, and passing thegaseous fluid mixture through a magnetic field whereby electric currentflows through said gaseous mixture.

3. A method of generating electric power, which comprises the step-s ofconducting a gaseous fluid along a flow path, injecting into saidgaseous fluid a first material whose atoms have at least one metastableenergy level to which said atoms are. raised after injection of saidfirst. material into said gaseous fluid, injecting an easily ionizablesecond material into said gaseous fluid after said atoms of said firstmaterial have been raised to said metastable level whereby atoms of saidsecond material are ionized by collisions with atoms of said firstmaterial in said metastable level, and passing the gaseous fluid mixturethrough a magnetic field whereby electric current flows through saidgaseous mixture.

4. A method of generating electric power, which comfluid, means forinjecting into the gaseous fluid a first material whose atoms have atleast one metastable energy level to which level said atoms are raisedin the gaseous medium, and means for injecting into the gaseous fluidafter said atoms of said first material have been raised to saidmetastable level an ionizable second material having an ionizationenergy level comparable to said metastable energy level of said firstmaterial, whereby atoms of said second material are ionized bycollisions with atoms of said first material in said metastable level.

References Cited in the file of this patent UNITED STATES PATENTSRudenberg June 18, 1929 OTHER REFERENCES

1. A METHOD OF GENERATING ELECTRIC POWER, WHICH COMPRISES THE STEPS OFCONDUCTING A GASEOUS FLUD ALONG A FLOW PATH, INJECTING INTO SAID GASEOUSFLUID A FIRST MATERIAL WHOSE ATOMS HAVE AT LEAST OE METASTABLE ENERGYLEVEL, RAISING THE ENERGY LEVEL OF ATOMS OF SAID FIRST MATERIAL TO THEIRMETASTABLE LEVEL, INJECTING AN EASILY IONIZABLE SECOND MATERIAL INTOSAID GASEOUS FLUID AFTER SAID ATOMS OF SAID FIRST MATERIAL HAVE BEENRAISED TO A METASTABLE LEVEL WHEREBY ATMS OF SAID SECND MATERIAL AREIONIZED BY COLLISIONS WITH ATOMS OF SAID FIRST MATERIAL IN SAIDMETASTABLE LEVEL, AND PASSING THE GASEOUS FLUID MIXTURE THROUGH AMAGNETIC FIELD WHEREBY ELECTRIC CURRENT FLOWS THROUGH SAID GASEOUSMIXTURE.